In mobile multihop ad-hoc radio networks, connectivity considerably varies in time and in space. By connectivity, is meant the possibility of a node of accessing the radio resource in order to transmit, without any perturbation, a signal and the possibility of the other nodes of accessing the resource at the same instant for receiving the transmitted signal.
These problems are exacerbated in a case of a strong node density.
Among ad-hoc radio networks, networks applying a routing protocol are known.
However in order to maintain a view of the topology of the network at each instant, these networks require constant updating of the mapping of the topology, as well as a propagation of the corresponding pieces of information through the network by means of suitable signaling packets. For high density networks, maintaining such a mapping becomes extremely difficult and complicated to apply. The signaling packets further limit connectivity.
Ad-hoc radio networks are also known which not require any routing protocol. These are multi-hop ad-hoc radio networks applying a broadcasting service of the flooding type.
Generally in an ad-hoc radio network, each node may act not only as a transmitter or receiver of a data packet, but also as a relay for a data packet between the transmitter and the addressee.
In this context, various services for broadcasting data packets may be applied.
A simple-to-apply broadcasting service is a service of a flooding type, wherein a transmitter wishes to exchange data with an addressee, transmits a message including the datum towards the whole of his neighbors, i.e. the whole of the nodes within the radio which of the transmitter. In turn, each neighboring node, acting as a relay, transmits a message including this datum to the whole of its neighbors. Step by step, the datum is broadcast into the whole network. It ends inter alia by reaching the desired addressee.
However, in the case of a high density ad-hoc radio network, a broadcasting service of the flooding type, in which everybody transmits to everybody, is not suitable because of the large number of packets transmitted and retransmitted by the different nodes for broadcasting a single datum. Therefore there is a high probability of a collision of the signals and degradation of the connectivity.
For a mobile and high density multihop ad-hoc radio network, document EP 2 440 001 A1, incorporated by reference, discloses a node including a control means for accessing the radio resource (MAC according to the acronym “Medium Access Control”) applying a dynamic containment method for accessing the resources.
More specifically, the various nodes of the network are synchronized. The access to the radio resource is subdivided into time frames. A node is allowed to access the resource every Q frames. The period Q is variable and its value is dynamically adapted according to the use of the resource made by the relevant node and its neighbors. Further, a frame is subdivided into a plurality of time slots. In an authorized frame, a node is able to randomly select the slot in which it transmits a data packet.
Thus, in document EP 2 440 001 A1, each node is able to estimate the number of neighboring nodes V depending on the number of collisions detected in the different slots of a plurality of successive frames. When the estimated number of neighbors V increases, the node asks its neighbors to increase their transmission periods Q.
However, in high density ad-hoc radio networks applying a broadcasting service of a flooding type, the application of a network for containment of packets may not be sufficient.